This application claims the benefit of Japanese Application No. 2000-172415, filed on Jun. 8, 2000, which is hereby incorporated by reference.
1. Field of the Invention
This invention relates to a direct injection type internal combustion engine that sequentially repeats a first compression stroke, a first expansion stroke, a second compression stroke, and a second expansion stroke with the rotation of a crank shaft of the engine.
2. Description of Related Art
In recent years, an internal combustion that improves a combustion cycle to achieve a high efficiency and the purification of exhaust gases has been developed.
For example, Japanese Patent Provisional Publication No. 9-4459 discloses an engine that has a main combustion chamber and a sub combustion chamber, each of which is provided with a spark plug. This engine aims at improving a stoichiometrical thermal efficiency by performing two expansion strokes in one compression stroke in such a manner that a main combustion chamber (main chamber) and a sub combustion chamber (sub chamber) ignite the interior mixture by respective spark plugs to perform combustion independently from each other.
In the above prior art, there is the necessity of providing the sub combustion chamber in addition to the normally-provided combustion chamber (main combustion chamber) and providing a spark plug in each of the main combustion chamber and the sub combustion chamber. This complicates the structure of the engine and requires a very high manufacturing cost. Moreover, the prior art is not so different from the normal internal combustion engines with respect to the exhaust gas characteristics because the main chamber mixture and the sub chamber mixture are only burned in different timings in order to perform two expansion strokes in one compression stroke.
It is therefore an object of the present invention to provide a direct injection type internal combustion engine that improves fuel economy and purifies exhaust gases in a more refined manner without significantly increasing a manufacturing cost.
To attain the above object, the present invention provides a direct injection type internal combustion engine comprising: an intake and exhaust mechanism for taking in and exhausting air for a predetermined period of time between a second half of a second expansion stroke and a first half of a first compression stroke following the second expansion stroke so that the first compression stroke, a first expansion stroke, a second compression stroke, and the second expansion stroke can be repeated sequentially with rotation of a crank shaft in the internal combustion engine; a control device for controlling injection of fuel supplied to at least a combustion chamber in the internal combustion engine; and the control device for carrying out a controlling operation to inject first fuel in one of the first compression stroke and inject second fuel in one of the first expansion stroke and the second compression stroke.